U.S. Secretary of State Hillary Clinton says the United States is focusing sanctions on Iran's Revolutionary Guard Corps, asserting that the elite unit has become too involved in security, political and economic decisions.

Clinton told VOA Tuesday that Iran is becoming a more belligerent and repressive nation as the Revolutionary Guard increases its influence.

Clinton suggested the power shift from clerical and political leaders to the Revolutionary Guard may stem from Iran's inner turmoil that resulted from President Mahmoud Ahmadinejad's disputed re-election in June.

Iranian Foreign Minister Manouchehr Mottaki criticized Clinton for saying Monday that Iran has become a "military dictatorship." He accused the U.S. of being like a military dictatorship through its actions in Iraq and Afghanistan.

Clinton also warned that Iran may trigger a nuclear arms race in the Middle East if it obtains an atomic weapon.

In a speech Tuesday at a women's college in Jeddah, Saudi Arabia, Clinton said evidence does not support Iran's claim that its nuclear program is being developed for peaceful purposes only.

President Ahmadinejad responded by saying he does not take Clinton's comments seriously.

On the Middle East peace process, Clinton said it is imperative to remain optimistic about resolving the Israeli-Palestinian conflict. She said both sides have so much at stake and will eventually realize it is in their best interest to return to the negotiating table.

Clinton spoke at the end of a tour of Persian Gulf states, where she sought to gain support from U.S. allies for tougher sanctions on Iran.